Try gunparts.com, or see what's in Shotgun News. A stock shouldn't be too hard to find, many of the old house brands had some interchangeability.
Also, do your loved ones a favor and have that shotgun checked by a qualified smith before touching off any rounds even if you've fired it recently w/o ill effect. Some of the old, cheap shotguns made 1880-1920 or so aren't as safe and well made as we'd like them to be.
Also, some of these have the old 2 1/2 or 2 9/16 chambers,and using modern 2 3/4" or 3 inch ammo can be like holding a grenade in front of your face and discarding the pin.
